The invention concerns a valve train of an internal combustion engine comprising a switchable, rotationally symmetrical component such as a cam follower or a support element for a lever-type cam follower, said component comprising a housing that is mounted with an outer peripheral surface in a bore connected to the internal combustion engine, said component further comprising a cavity which encloses an inner element that is axially displaceable relative to the housing, a coupling element being provided in the housing for coupling the inner element and the housing in a relative position to each other, an anti-rotation device in form of a first body that projects radially beyond the housing being guided in a first longitudinal groove of the bore of the internal combustion engine.
A generic valve train of the pre-cited type is disclosed in DE 199 155 31 A1. This proposes a switchable cam follower for activating a tappet push rod. The anti-rotation device of this cam follower is a body, identified at (27), that projects beyond a housing. With regard to its size, its weight and particularly with regard to its overall outer appearance, this cam follower does not differ, or differs only slightly, from non-switchable cam followers. Therefore, in a combined installation of switchable and non-switchable cam followers in bores of internal combustion engines or cylinder heads there is a danger of confusion of parts and the risk of wrong installation.
It is an object of the invention to provide a valve train of the pre-cited type in which the aforesaid drawback is eliminated.
This and other objects and advantages of the invention will become obvious from the following detailed description.
The invention achieves the above objects by the fact that a second, pin-like body acting as a mounting safety device is arranged in a through-bore of the housing, and extends radially inward and outward beyond the housing, said second body being guided with an outer section in a second longitudinal groove of the bore of the internal combustion engine, and the cavity of the housing comprises in a peripheral portion in which the second body is arranged, a material reduction such as an annular groove into which an inner section of the second body extends.
In this way, a simple mounting safety device for the switchable component is obtained. At the same time, only slight structural modifications have to be made to the component for the arrangement of the novel mounting safety device. The drawback of confusion of switchable with non-switchable components is eliminated. Due to the configuration of the internal combustion engine with the second longitudinal groove for the component, switchable components with their second body, in particular, can no longer be installed in bores for non-switchable components. To put it differently, the engine fitter also recognizes, due to the presence of the second longitudinal groove, the incorrect arrangement if non-switchable components are wrongly mounted in bores for switchable components.
Another advantage of the claimed configuration of the annular groove in the housing for an inner section of the second body, is that the total mass of the housing and, thus also, of the component can be reduced.
According to a preferred embodiment of the invention, the second body can be made, for example, of a plastic, which, if desired may be colored or provided with a color coating or at least be colorable. This elastic body can be installed in the through-bore of the housing in a simple manner, for example, by a proposed snap or clip connection. Due to the color contrast of the second body with the housing, for example, by using a striking color like yellow or red, a further, special protection from confusion during mounting is obtained.
It is further proposed to provide at least one longitudinal slot in the second body. This measure enables it to be easily pressed together during assembly and facilitates its arrangement in the through-bore.
According to a further proposition of the invention, the second body is arranged at a relatively high level in the region of an edge of the housing beyond which the inner element projects. As a result, the second longitudinal groove in the internal combustion engine requires only a small axial depth which advantageously reduces manufacturing costs. Further, the geometry of the second longitudinal groove can be chosen relatively freely because it surrounds the outer peripheral surface of the second body with clearance. This means that its shape must not necessarily be complementary to the outer peripheral surface of the second body.
Due to the proposed pin-like geometry of the second body, it is simple to make and its positioning in the through-bore of the housing does not pose any great production problems.
Although a preferred means for fixing the second body in the housing is a snap or clip connection, it is also conceivable to use other fixing measures such as screwing, pressing-in or gluing and the like. It is understood that a person skilled in the art will also think of geometrical shapes for the second body other than the pin-like shape proposed by the invention.
Advantageously, the proposed snap connection of the second body to the housing has no repercussions whatever on the housing and can be realized in a simple and economic manner.
Although the invention particularly proposes only one body as a mounting safety device and only one body as an anti-rotation device, a plurality of these may be used on a single component.
The component envisaged is particularly a roller or a mushroom tappet that follows a cam of a bottom camshaft and acts on a tappet push rod. However, the measures proposed by the invention can also be used, for example, on a cup tappet of a direct-acting type or on a support element of a lever-type cam follower.
The invention will now be described more closely with reference to the appended drawings.